The tremendous growth in multimedia products and services through the Internet has led to the need for copyright protection, authentication and integrity of data. In the past few years, a number of digital watermarking techniques have been developed and patents granted, for the purpose of resolving the legal use or misuse of copyright information on the Internet. Unlike data encryption that transforms the original data to another form for security transmission, digital watermarking embeds an invisible or inaudible watermark directly into the original data.
Typical examples of recent work in the field of digital watermarking or data embedding are described in U.S. Pat. No. 5,636,292 to Rhoads (1997) and U.S. Pat. No. 5,659,726 to Sandford and Handel (1997). Rhoads discloses methods for embedding an identification code on a carrier signal, such as an electronic data signal or a physical medium. Sandford and Handel disclose a method of embedding auxiliary information into a set of host data, such as a photograph, or a television signal.
Prior art publications in the field of digital watermarking technology, including the two aforementioned granted U.S. Patents, generally envisage only the embedding of a very limited number of bits of information (in the form of binary digits ‘1’ and ‘0’) or a few characters (such as ‘A12’) into the carrier signal. More detailed ownership information requires a higher level of embedded watermark information either in the form of longer alphanumeric character strings or, if possible, trademarks/logo images, or speech of the original owner, which is embedded into and retrieved from the carrier signal. However, this has previously been considered to be very difficult to achieve, without significant corruption of the data being labelled as the amount of data to be inserted is increased. The present invention describes such a method for embedding digital audio or image watermarks directly into targeted audio or image data, substantially inaudibly or invisibly, respectively.
There are many other potential consumer, commercial and service applications that can benefit from the use of digital watermarking technology in copyright protection and security transmission. These applications include the embedding of owner identification, such as the trademarks or logos of an owner into digital still and video cameras, or copyright protection and royalty tracking monitoring of sound recordings in the music industry with digital audio watermarks of the artists' voice embedded into the sound tracks.
Furthermore, commercial and service sectors are also interested in the secure transmission and reception of sensitive messages, data, and even images that could be camouflaged into normal data streams transmitted over an open channel.